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Capstan Head Lathe.


First the drill is clamped in a V groove made in the support
A, and is held in the proper position by means of the plate B
placed at the front end of the groove. The support A rides
on a guide-arm c, which, in plan, is set at an angle of 59°,
or half the angle of the drill. This allows the surface of the
drill point to lie parallel to that of the emery wheel a The
hand-wheel E serves to bring the drill to the wheel, and F turns
a screw for the purpose of taking up various surfaces of the
wheel so as to produce equal wear. G is a fulcrum, supporting
a rocking arm, which, in turn, carries a horizontal arm H. One
end of H encloses the emery wheel spindle, and the other is pinned
to the rotating disc j. It follows, therefore, that if the disc j be
turned left-handed by taking hold of the handle K, the rocking
arm will deviate to the front, and the centre of the emery wheel
will describe the approximate hyperbola required to be ground off
the drill point, as shewn by the dotted lines in elevation. By
fixing the fulcrum G at slightly varying heights by means of the
hand lever L, it is possible to obtain sufficient variation in the drill
curve to suit various sizes of drills; and, as the driving strap is
changed in position, it is kept tight by the jockey pulley N
provided with a balance weight. When using the machine the
workman takes hold of the handles M and K, and pulls K towards
him, and after one surface of the drill has been ground the latter
is turned round in the V groove, and the opposite surface trued
up, B then serving to register the second position with the first.

The Capstan or Turret Head.—Although we were
supposed to have completed our descriptions of machine tools in
Chapter V., our work would be incomplete without an account of
this very important labour-saving appliance. The lathe in Fig. 214
is shewn supplied with both Capstan-Head Slide Rest, and Screw-
Copying apparatus, and is designed by Selig, Sonnenthal & Co.
A is the head, which is capable of holding six tools, to be used in
succession on th^work in the lathe. These are placed in position
by releasing a catch E, turning the head by hand, allowing catch E to
return to its place by means of a spring, and finally clamping the
rest firmly by means of the lever D ; all this occupying but a very
short space of time. Of course, it may often be necessary to use
both slides to put the tools in position, as will be seen, and the